[Pharo-users] Peeking at a stream

I sometimes find, when working with a stream, that I need to "peek ahead” a few items, without disturbing the state of the stream. The message stream peek gives me the next item, but doesn’t generalize to multiple items, So I end up writing code like this: findSomething | savedPosition result | savedPosition := stream position. stream position: start. “code involving various manipulations of stream, including stream next" result := stream position + 1. stream position: savedPosition. ^ result This code involves at least two temps, is not very easy to read, and risks not resetting the stream properly if I do a return. It seems to me that a better solution would be what Kent Beck calls an “execute around” method: findSomething ^ stream unchangedDuring: [ :s | “code involving various manipulations of stream, including stream next" stream position + 1 ] I’m not sure that I like the name #unchangedDuring:; perhaps you can think of a better one? The implementation of this would be PositionableStream >> #unchangedDuring: aBlock "execute aBlock with self as argument. Ensure that when this method returns, I still have my current state." | savedPosition | savedPosition := self position. ^ [ aBlock value: self ] ensure: [ self position: savedPosition ] or perhaps PositionableStream >> #unchangedDuring: aBlock "execute aBlock with self as argument. Ensure that when this method returns, I still have my current state." ^ [ aBlock value: self copy ] which might be better in the case that the stream is a file stream and aBlock causes the buffer to be refreshed from the disk. Do other Smalltalks have a method like this? Does it already exist in Pharo, somewhere that I’ve failed to look? Would it be a worthwhile addition to Pharo? What would be a good name?